Free DSST Astronomy Practice Questions

Sample Practice Questions

Try these 10 sample questions from the DSST Astronomy practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which statement best describes a hypothesis used in scientific research?

   1. A.A testable possible explanation of a natural phenomenonCorrect answer: A
   2. B.A measurement that has already ruled out every explanation
   3. C.A universally accepted conclusion that cannot be reconsidered
   4. D.A description that requires no connection to observations

   Explanation: NASA states: "a hypothesis (a statement of a possible explanation for some natural phenomenon), which can then be tested and retested" This supports the selected answer.

   Reference: Scientific Consensus — Scientific Consensus, discussion of hypotheses and theories

2. 2In Kepler's first law, where is the Sun located relative to a planet's noncircular elliptical orbit?

   1. A.At the center of the ellipse
   2. B.At one focus of the ellipseCorrect answer: B
   3. C.At the end of the minor axis
   4. D.At both foci of the ellipse

   Explanation: NASA states: "Each planet's orbit about the Sun is an ellipse. The Sun's center is always located at one focus of the ellipse." The first law places the Sun at one focus; the center and axes do not generally coincide with a focus.

   Reference: Orbits and Kepler’s Laws — Basic Properties of Ellipses and Kepler's Three Laws

3. 3How is the precession of Earth's rotation axis described?

   1. A.The daily spin of Earth around its axis
   2. B.The yearly revolution of Earth around the Sun
   3. C.The slow change in direction of Earth's rotation axisCorrect answer: C
   4. D.The monthly revolution of the Moon around Earth

   Explanation: The source states: "This precession causes the axis of Earth to describe a circle having a 23.4 degree radius relative to a fixed point in space over about 26,000 years" Precession changes the axis direction slowly over millennia.

   Reference: Chapter 2: Reference Systems — Precession of Earth's Axis Over 26,000 Years

4. 4Among radio, infrared, visible and ultraviolet light, which has the highest frequency?

   1. A.Radio
   2. B.Infrared
   3. C.Visible
   4. D.UltravioletCorrect answer: D

   Explanation: NASA orders the spectrum: "Gamma rays, X-rays, ultraviolet light, visible light (the visible rainbow), infrared light, microwaves, and radio waves are all forms of light (also called electromagnetic radiation)." NASA also states: "Wavelength, represented by the Greek lower case lambda (λ), is equal to the speed of light (c) divided by frequency (f)." Ultraviolet has the shortest wavelength of these choices and thus the highest frequency.

   Reference: The Electromagnetic Spectrum — The Electromagnetic Spectrum

5. 5Which of the following planets is classified as terrestrial?

   1. A.Saturn
   2. B.Neptune
   3. C.Jupiter
   4. D.MarsCorrect answer: D

   Explanation: NASA states: "the first four planets – Mercury, Venus, Earth, and Mars – are terrestrial planets." Mars is one of the four rocky inner planets.

   Reference: Solar System Facts — Size and Distance; Formation

6. 6Which layer of the Sun is the visible surface seen from Earth?

   1. A.The core
   2. B.The photosphereCorrect answer: B
   3. C.The radiative zone
   4. D.The convection zone

   Explanation: NASA states: "The part of the Sun commonly called its surface is the photosphere." The photosphere emits much of the visible light seen from Earth.

   Reference: Sun Facts — Structure, photosphere

7. 7What type of galaxy is the Milky Way?

   1. A.Elliptical
   2. B.Barred spiralCorrect answer: B
   3. C.Irregular dwarf
   4. D.Ring galaxy

   Explanation: NASA states: "The Milky Way is a barred spiral galaxy" The Milky Way has a barred spiral structure.

   Reference: Universe glossary — Milky Way; galaxy; spiral and elliptical galaxy; parallax; parsec; Cepheid entries

8. 8Which component produces much of the diffuse X-ray emission from a galaxy cluster?

   1. A.Stars within the member galaxies
   2. B.Hot plasma between the galaxiesCorrect answer: B
   3. C.Dark matter surrounding the cluster
   4. D.Cool dust between the galaxies

   Explanation: NASA states: "Hot plasma accounts for another 15% of its mass and makes them bright X-ray sources." The hot intracluster plasma emits X-rays.

   Reference: Universe glossary — Galaxy cluster

9. 9What distinguishes a scientific theory from a single hypothesis?

   1. A.A theory is a raw measurement rather than an explanation.
   2. B.A theory can integrate hypotheses into a general explanation.Correct answer: B
   3. C.A theory becomes valid only when it cannot be tested.
   4. D.A theory is simply a personal opinion about observations.

   Explanation: NASA states: "a group of hypotheses might be integrated and generalized into a scientific theory" This supports the selected answer.

   Reference: Scientific Consensus — Scientific Consensus, discussion of hypotheses and theories

10. 10What does Kepler's second law say about a line connecting a planet to the Sun?

    1. A.It sweeps equal angles in equal times.
    2. B.It sweeps equal distances in equal times.
    3. C.It sweeps equal areas in equal times.Correct answer: C
    4. D.It sweeps equal areas in equal angles.

    Explanation: NASA states: "The imaginary line joining a planet and the Sun sweeps out – or covers – equal areas of space during equal time intervals as the planet orbits." The law compares areas over equal time intervals.

    Reference: Orbits and Kepler’s Laws — Basic Properties of Ellipses and Kepler's Three Laws